[Updated for QLab 4.1 13 JUL 2017 ]
The Devamp cue is very important in allowing sound and video designers to follow the timing of performers, rather than performers having to tailor their performances to preset timings. This example uses audio cues, but you can do exactly the same thing with video loops.
The origins of the technique go back beyond Vaudeville. Imagine a man balancing a chair on his nose. It might take anything from ten to twenty-five seconds for him to have it balanced, during which the orchestra would ‘vamp till ready’ round some drum rolls and tremulando strings . When the chair was stable the music would change seamlessly to triumphant chords. Sometimes the performer would manage 10s before the chair fell, on a good day it might be more than a minute, , so again the music would vamp until ready until the chair fell, was caught and the music seamlessly transitioned to a double tempo for playoff.
Here’s a video of a simple vamp sequence, using 2 loops of drums and a final cymbal splash.
How It Works: Cue 1 is set to an infinite loop
Cue 2 is a ‘start first child and go to next cue’ group. It contains: A devamp cue targeting cue 1 and set to start the next cue and stop it’s target cue. When cue 2 is fired, it waits for cue 1 to complete the current iteration of the audio loop it is playing, and then fires the next cue,, i.e. another looped audio cue, Loop 1.wav and stops cue 1.
Cue 3 is similar. The cymbal crash is the coda to this cue sequence, and only plays once, it is not looped. This works very well, but if the devamp cue was given when the loop had just started, we would be waiting for nearly 8 beats, (over 3 seconds at this tempo), before the sequence advanced to the next loop. Here’s a video of the same sequence but this time the programming allows the devamp to trigger either at the end of each 4 beat, 2 beat, or 1 beat phrase of the currently running cue. This makes it’s operation similar to the quantise feature in Ableton Live.
How It Works: All the examples in the video use a second audio cue, with it’s volume out i.e. muted, in each group, running alongside the audio cue we can hear. The length of this muted cue is set to a fraction of the length of the 8 beat phrase we are revamping. e.g in the second example where we revamp after 2 beats the length of the dummy, muted cue is 1/4 of the length of the audible cue.
The silent cue is used as the devamp. It is also necessary to add a cue to fade and stop the audible cue, as this is no longer the target of the devamp and will not be stopped by it.
Method 2: This video shows a different method of devamping. There is only one audio cue which is sliced. The devamps tell the playhead to continue when it reaches the next slice, instead of performing the loop if present.
In this example, in the workspace, I have decoupled the playhead from the selection, in order to display the sliced waveform, so you can observe it while other cues are run. When the playhead is decoupled, the highlight stays on the selected cue which is displayed in the inspector, and the playhead is just the white arrow head on the left hand side of the cuelist. I have used an OSC command in the example workspace, but you can also set this from settings/general in QLab. I reset it at the end of this example, but if you need to reset it manually you can press 1 which will trigger a script to reinstate ‘selection follows playhead’.
The final example here demonstrates, that as well as devamping loops, the slices can also be used to trigger other events.
The slices all have their play counts set to 1, so the audio cue plays straight through. Every time a slice marker is encountered a cue is triggered which plays all the cues in a fire all group named DO THESE CUES ON SLICE. This group can contain any cues you like; MSC to fire a lighting board, video cues, subtitles etc. In the example, just to make clear that a cue is happening, an audio cue is fired on each slice with a spoken GO announcement. Each DO THESE CUES group also contains the cue which triggers the next devamp. This is delayed by a tenth of a second to allow the playhead time to pass the marker before it sets the next devamp.
Here is the cue in action:
In the workspace there is one further example that has all the slices reset to loop, and allows the revamps to be cued manually. The DO THESE CUES group is fired as before on each devamp.
You can download a workspace containing all the examples here
The drum loop used in the examples is by v0idation distributed under a Creative Commons 0 license (public domain). The chapter graphic is by Mic Pool. All rights reserved.